Antenna system



July 6, 1943. A. B. BAILEY ANTENNA SYSTEM Filed Jan. 26, 1940 2Sheets-Sheet 1 VGF INVENTOR AB. BAILEY ATTORNEY July 6, 1943.

A.B.BAmY

ANTENNA SYSTEM Filed Jan. 26, 1940 T0 TRANSMITTER 0R RAD/0 RECEIVER 2SheetsSheet 2 5 moan/0 0R fi/nALL/c poor IN VEN TOR AB BAILEY ATTORNEVPatented July 6, 1943 ANTENNA SYSTEM Arnold E. Bailey, New York, N. Y.,assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y.,a corporation of New York Application January 26, 1940, Serial No.315,632

7 Claims.

This invention relates to antenna systems and more particularly to anarray especially suitable for use with ultra-short waves.

One antenna array in common use today comprises several half waveradiators colinearly arranged in a vertical or horizontal plane andenergized in phase, and means such as a half wave coil or a quarter waveline loop included between the adjacent radiators for suppressing theradiant action produced by standing Wave alternations or loops having aphase opposite to that of the effective radiating alternations. Sincethe radiators, or collectors, are ordinarily connected in series, thetotal attenuation is relatively high and, as a result, the amplitudes ofthe outgoing and return traveling waves, and of the resultant standingwave, are not as large as desired. Moreover, the half wave suppressorsand the associated supporting structure usually employed are such as tonecessitate an undesired physical separation between the adjacentradiators or collectors whereby a highly concentrated low fire beam ormaximum directive lobe is not fully realized. Again, in arrays of thistype the radiation or absorption by the line and, in some systems, theradiant action of supporting structures such as guide wires, oftenmaterially distort the array directive characteristic and unfavorablyaffect the array efficiency.

It is one object of this invention to secure maximum radiant action in adesired direction.

It is another object of this invention to secure uniform maximum radiantaction in all directions included in a given plane.

It is still another object of this invention to secure a highlyconcentrated radio beam and to avoid distortion thereof by lineradiation.

It is a further object of this invention to secure a highly directional,compact self-supporting antenna array.

According to one embodiment of this invention the array comprises avertical tubular member a plurality of half wave-lengths long, aplurality of quarter wave-length cylindrical sleeves of greaterdiameter, the sleeves being coaxially related to the tubular member andspaced thereon a quarter wave-length apart and means, such as bushings,connecting the inner circumference at the upper end of each sleeve tothe rigid vertical member. Preferably, the diameters of the lineartubular member and associated sleeves are graduated or stepped in adirection toward the top of the structure. A transmission line innerconductor is included within and coaxially related to the tubularmember; and the inner line conductor and the inside surface of thetubular member constitute a coaxial line. In operation, the outersurface of each quarter Wave-length sleeve and the one-quarterWave-length exposed portion of the tubular member immediately aboveconstitute a dipole; and the inner surface of each sleeve and theportion of the outer surface of the tubular member enclosed therebyfunction as a radiation suppressor. Thus, the radiation produced by oneset of standing Wave alternations is canceled and since the adjacentin-phase alternations on the radiating portions of the structure arevery closely positioned a highly concentrated beam is produced.Preferably individual branch line conductors are provided from theenclosed inner line conductor to several sleeve members whereby ineffect the radiating elements are connected in parallel and a strongstanding wave is established on the radiating portions of the structure.In one practical embodiment, branch line conductors are associated withalternate sleeve members, beginning with the top sleeve, the point ofconnection on the sleeve being critically selected and such that thebranch line and antenna impedances are matched. The connection to thetop sleeve is approximately a quarter wavelength from the apex of thetubular mast and the top extremity of the inner conductor is connectedthrough a metallic cap or top end-piece to a point near the uppermostextremity of the tubular member, whereby the portion of the line abovethe last branch conductor constituted by the inner line conductor andthe inner surface of the mast forms a high impedance shortcircuitedquarter Wave transformer and functions as if removed. The lowestextremity of the inner line conductor is similarly connected through ametallic plate or bottom end-piece to the other extremity of the mastand the inner conductor of the main low impedance coaxial line from thetransmitter or receiver is adjustably connected to the inner conductorat a distance slightly less thana quarter wave-length from the platewhereby the line section comprising the lower portion of the innerconductor and the associated inner surface of the mast functions as animpedance transformer to match the impedances of the two coaxial lines.

The invention will be more fully understood from a perusal of thefollowing discussion taken in connection with the drawings on which likereference characters denote elements of similar function and on which:

Figs. 1 and 2 illustrate, respectively, elevational and sectional viewsof a simple embodiment of the invention;

Fig. 3 illustrates a sectional view of another embodiment;

Fig. 4 illustrates a tower antenna array constructed in accordance withthe invention and Fig. 5 is a perspective view of a half wave suppressorincluded in the system of Fig. 4;

Figs. 6 and '7 illustrate, respectively, perspective and sectional viewsof a preferred embodiment of the invention.

Referring to Figs. 1 and 2, reference numeral l denotes a rigid solidcylindrical antenna member a plurality of one-half wave-lengths long andpositioned in a desired plane of wave polarization as, for example, thevertical plane. Reference numerals 2 designate sleeve type metallic halfwave suppressors each one-quarter wave-length long and supported bymember I through metallic bushings 3. The tubular sleeves 2 and thelinear member I are coaxially related and the sleeves are spacedone-quarter wave-length apart along the member I, the uppermost quarterwavelength section of the member I being exposed. A translation device4, such as a transmitter or receiver, is connected by conductors 5 and 6of line 1 between the lowest sleeve and the adjacent portion of memberI. The linear array may be supported on a ground plate or on top of astructure or pole 8 and while the linear array is a plurality of halfwave-lengths long the supporting pole or structure may, of course, haveany height or length. Since in operation the velocity of the current onmetallic members i and 2 is slightly less than that of a wave in space,that is, less than the theoretical velocity of wave propagation, thelength of each sleeve and the sleeve spacing are each lightly less thana theoretical quarter wave-length.

In operation, assuming the device 4 is a transmitter, current flowsalong the outer surfaces 9 of sleeve 2, exposed surface Ill of bushing3, exposed surface H of member I, concealed surface l2 of member I andinner surfaces I3 and M, respectively, of bushing 3 and sleeve 4, asindicated by the line IS in Fig.2. As is known, the current on theexposed surface 9 of sleeve 2 and the current on the inner surface l4are sepa rate and distinct, as explained in Patent 2,258,953 to W. H. C.Higgins, granted October 14, 1941. Thus a standing wave having similarlyphased alternations I6 is established on the exposed radiating surfacesof members i and 2 and the oppositely phased alternations i! arerendered ineffective in so far as radiant action is concerned. Theconducting surfaces I2, l3 and I4 constituting the half wave suppressoris electrically similar to a half wave-length conductor folded at thecenter and back on itself; and the exposed colinear radiating surfaces 9and II form a plurality of in-phase dipole radiators l8. It will benoted that the construction and design of the phase suppressors are suchas not to necessitate a physical separation between adjacent in-phasedipoles. Consequently, the effective alternations are closely adjacentand their nodal points are in effect superimposed whereby a highlyconcentrated field is emitted and, at a given distant receiving point,the field components corresponding to the several dipoles are more nearlin phase agreement than in the case of the prior art system mentionedabove wherein the dipoles are physically separated. Theoretically, thecurrent at each nodal point has zero amplitude but it has been found inpractice that at the intermediate nodal points waves of small amplitudeare established.

Referring to Fig. 3, the member I is hollow and encloses a low impedancecoaxial line 20 having an inner conductor 2| and an outer conductor '22,the line 20 and the member I being coaxially related. Reference numerals23 denote stand-off insulators for maintaining the sleeves 2 in positionand numerals 24 designate metal bushings for supportin line 20, onebushing 24 being included between the top extremity of conductor 22 andthe member I. The inner conductor 2! of line 20 is directly connected byseparate branch line conductors 25 to alternate sleeves 2. Preferablythe outer conductor 22 and one terminal of device 4 are connected toground 26 by conductor 21.

The radiant operation of the system of Fig. 3 is substantially the sameas that of Fig. 1. The effective or radiant standing wave alternationsestablished on each dipole I8 are relatively strong and have intensitiescomparable to those established on the structure of Fig. 1 since thedipoles are similarly energized in parallel, each through a path of lowimpedance. In the system of Fig. 1 the dipoles are energized in series,and the standing wave on the top dipole l8 which receives its energythrough the high impedance lower dipoles is considerably weaker thanthat, for example, on the lowest dipole directly connected to the lowimpedance line I. By positioning the line 20 within the member i andplacing the short branch line conductors 25 inside sleeves 2, theformation of undesired standing waves on the outer surface of conductor22 and the consequent distortion of the array directive characteristicby line radiation are substantially prevented. Hence, in accordance withone feature of the invention, in an array comprising a plurality ofantenna elements connected in parallel, all transmission line conductorsadjacent the structure are effectively shielded by the array elements.The arrays of Figs. 1, 2 and 3 are, of course, equally suitable forreceiving and transmitting and may comprise any practical number ofdipole elements. Also, these arrays may be oriented for any desiredpolarization and they are each suitable for use in stationary or mobileradio systems.

Referring to Figs. 4 and 5, the member 30 is a conventional tapered mastor tower type antenna element a plurality of wave-lengths long, and thephase suppressors each comprise the inner conductor surface 3| of thecage 32 and the associated enclosed surface 33 of the tower antenna 30.The cage radiator-suppressor 32 comprises a top annular member or hoop34, bottom annular member 35, longitudinal members 36 and transversemembers 31. The transverse members 3'! correspond in function to thebushings 3 of the systems of Figs. 1, 2 and 3 and are rigidly fastenedto the tower 30. The cages 32 are placed a quarter wave-length apart andsince the tower or mast 3B is tapered they have different diameters asshown by Fig. 4. As in Fig. l the line I from the translation device 4is connected to the bottom cage 32 although, alternatively, the line mayextend inside the tower and parallel connections to the several cagesmay be used as in the system of Fig. 3. The operation of the system ofFig. 4 is similar to that of the systems of Figs. 1, 2 or Fig. 3 and inview of the above discussion is believed to be apparent.

Referring to Figs. 6 and '7 reference numeral M] denotes a flagpole typeradiator comprising the iron pipe sections 4|, each approximately aquarter wave-length long and having different diameters. The sectionsare arranged so that the diameter of the mast decreases toward the topin steps. The junctions of the adjacent sections are telescoped andcalked to prevent moisture from entering the tubular iron conductor and,preferably, the arrangement or construction at each junction is suchthat if necessary, as upon a change in assigned operating frequency, thelength in meters of each section 4| and the overall height of thestructure may be altered. Reference numerals 42 designate light-weightmetallic sleeve members which are spaced a quarter wave-length apart andsupported on the member 40 by metallic bushings 43 and stand-offinsulators 44. The diameters of the sleeves are graduated 01' stepped inaccordance with the different diameters of the member 40. As in thesystems described above, the uppermost quarter wave-length portion ofmember 40 is exposed and constitutes one-half of the top dipole I8.While Fig. 6 illustrates certain electrical and mechanical features of apreferred embodiment, in practice, the structure would usually be moreslender than that indicated by this figure. In one practical embodimentthe dipoles l8 are each sixteen feet long, the diameter of the topportion of radiator I is two inches, the sleeve diameter is one inchgreater than the diameter of the associated portion of member I, and thesleeve thickness is approximately one thirty-secondths of an inch.

A single line conductor 45 extends, coaxially, within member 40 and theinside surface 46 of member 40 constitutes a return line conductor.Branch conductors 41 are utilized to connect the line conductor 45directly to alternate sleeve members including the top sleeve. The innerconductor 45 extends a quarter wave-length above the point 48 at whichit is joined to the top branch line conductor 4? and it is conductivelyconnected to a point near the top extremity of member 40 and supportedby the top piece or cap 49. The lower terminal of the inner conductor 45is electrically connected through the plate or bottom piece 50 to thelower extremity of the member 45. Numeral denotes the main coaxial linefrom the translation device (not shown) the line having its outerconductor 52 connected to member 40 and its inner conductor 53adjustably connected to the inner conductor 45 at 'a point 54 which isless than a quarter wave-length above the bottom end-piece 58.Preferably, the line 5| is positioned below the ground surface or thebuilding roof 55. If desired, instead of insulators 44, the spacebetween the sleeves 42 and member 40 may be filled with an insulatingcompound for the purpose of securing a solid aerial structure.

The radiant operation of the array of Figs. 6 and '7 is substantiallythe same as that of the system of Figs. 1, 2 or Fig. 3. The line sectionformed by the portion of the inner conductor 45,

between junction point 54 and plate 50 and by the associated insidesurface 46 of member 40, constitutes an impedance transformer formatching the low impedance line 5| to the high impedance line comprisingthe inner conductor 45 and the inside irregular surface 46 of member 40,the proper adjustment or position for the junction point 54 beingdetermined by predetermined calculations or by experiment. At the upperend of the structure, the line section formed by the quarter wave-lengthportion of conductor 45 above junction point 48 and the associatedinside surface of member 4!] constitutes a high impedanceshort-circuited quarter wave transformer whereby this line sectionfunctions as if removed. In other words, while the inner conductor 45preferably extends for mechanical reasons to the top extremity of member46 or to cap 49, the coaxial line comprising conductor 45 does notextend, from an electrical standpoint, beyond the point 48. Thisself-supporting structure, Figs. 6 and 7, is suitable for use in groundstations and since it is self-supporting, it is especially suitable forutilization on top of build ings. It functions to produce a concentratedlow fire, beam of uniform intensity in all horizontal directions and ishighly efiicient for emission or reception of ultra-short waves. Ascompared to prior art systems, it is easily manufactured and installed,and more easily maintained in operation.

Although the invention has been described in connection with certainembodiments it should be understood that it is not to be limited t theparticular structures described inasmuch as other apparatus may besuccessfully employed without exceeding the scope of the invention.

What is claimed is:

1. In combination, a vertical tower antenna a plurality of halfwave-lengths high, a plurality of cage sections each a quarterwave-length long enclosing alternate quarter wave-length portions ofsaid tower including the second portion from the top, each sectioncomprising a pair of spaced horizontal annular conductors and aplurality of substantially parallel linear conductors connected to andextending between said annular conductors, the upper extremities of saidsections being conductively connected to said tower, and a line from atransmitter connected to the lowest section.

2. In combination, a vertical hollow self-supporting radiator aplurality of half wave-lengths long and having a circular cross-section,a plurality of hollow sleeve-like members each a quarter wave-lengthlong substantially and having a diameter greater than that of saidradiating member, a plurality of metallic bushing members eachconnecting the upper end of one of said members to said radiator, saidbushings being attached to points on said radiator approximateiy a halfwave-length apart, a line from a transmitter extending inside saidradiator and separate connections from points on said line a wave-lengthapart to a plurality of said members.

3. In combination, a vertical self-supporting radiator a plurality ofhalf Wave-lengths long and comprising a plurality of sections havingdifferent diameters, a plurality of sleeve members, said sections andsaid sleeves each being approximately a quarter wave-length long, saidmembers being spaced a quarter wave-length apart along said radiator andhaving diameters uniformly greater than the associated section, metallicbushings included between the uppermost portion of the sleeve member andthe associated section, a high impedance coaxial line comprising theinner surface of said radiator and a conductor supported within saidradiator, said conductor being connected to alternate sleeves, atransmitter, a low impedance line connecting said transmitter to thehigh impedance line, and an auxiliary coaxial line comprising a portionof said radiator and an extension of said conductor connected in shuntto said coaxial lines for matching said lines.

4. In an antenna system, a hollow vertical metallic element comprising aplurality of cy1in drical one-quarter wave-length sections, havingdifierent diameters, the diameters being stepped and the lowest sectionhaving the largest diameter, a separate one-quarter Wave-length sleevesurrounding each of one set of alternate sections and conductivelyconnected at its upper extremity to its respective section, a firstli-ne conductor extending coaxially within said element and beingconnected to at least two of said sleeves, and a second conductorconnecting said first conductor to a translation device.

5. An antenna system in accordance with claim 4, said second conductorextending through the wall of the lowest section and being connected tothe first conductor at a point a quarter wavelength approximately abovethe bottom extremity of said lowest section.

6. An antenna system in accordance with claim 4, the section adjacentthe top section being included in the said set of alternate sections,said first conductor being connected to a point in the top section andto a point on the sleeve associated with the section adjacent the topsection,

said points being electrically separated a quarter wave-length, wherebythe upper extremity of said conductor is rigidly supported by said topsection through a high impedance.

'7. A rugged vertical coaxial antenna system comprising a hollow linearmember a half wavelength long, a quarter wave-length cylindrical sleevesurrounding the bottom half of said member and attached at its upperextremity to the mid-point of said member, a line conductor extendingcoaxially within said member, said conductor being attached to anintermediate point in said sleeve and to an intermediate point in theupper half of said member, the conductive path connecting said pointsbeing a quarter Wavelength long whereby the impedances of said conductorand antenna are matched, and the connection between the upper portion ofsaid member and said conductor includes a high impedance.

ARNOLD B. BAILEY.

